Description of Work A number of field studies have shown that mayflies (Ephemeroptera) tend to be more sensitive than other benthic macroinvertebrate taxa to elevated levels of total dissolved solids in streams impacted by mining. Until relatively recently, difficulties with culturing have precluded the use of mayflies as laboratory toxicity testing organisms; however, researchers at Stroud Water Research Center have found parthenogenic species that readily reproduce under laboratory conditions, and researchers at the US EPA EERD laboratory have developed laboratory cultured diets for mayflies that will help to move toward standardization of methods. Recent efforts at the Illinois Natural History Survey built upon these efforts and [...]